1. Field of the Invention
This invention relates to an aircraft instrument for generating rate of climb information and more particularly to an aircraft instrument for generating rate of climb information including the rate of vertical air movement outside of the aircraft, the best speed to fly information, and including a correction for climb induced by control motion.
2. Description of the Prior Art
In prior U.S. Pat. No. 3,451,265 issued to the inventor, a fast response rate of climb or sink meter was disclosed in which pressure responsive diaphragm members were used in a unique and novel combination to generate rate of climb information as well as to correct for the rate of climb which is attributable to operation of the aircraft controls. The rate of climb apparatus in the aforesaid patent may be used in an aircraft where it is important for the pilot to determine the rate of climb of the aircraft due to the vertical motion of the air outside of the aircraft.
The vertical motion of the air outside of the aircraft (termed NETTO) may be derived by subtracting the polar sink of the aircraft from the generated rate of climb information. In this vertical air or NETTO mode of operation, if the air motion is not moving or is smooth, the rate of climb meter would read zero. Such information is desirable for the operator of the aircraft (which is usually a glider) since it helps the operator locate a thermal condition and to steer into areas of least sink (i.e. the downward movement of the air). When flying fast, it is much easier to judge the thermal strength of moving air when the meter reads the vertical velocity of the air outside the craft directly instead of the sum of the air vertical velocity plus the aircraft rate of sink.
These two types of meter readings (i.e. rate of climb and NETTO) are discussed in the literature accompanying the various models of the above patented invention. See "Description and Instructions for Netto Optimum Cruise Control Options for Ball Variometers Models 100, 101, and 200" published by the Ball Engineering Company, 2140 Kohler Drive, Boulder, Colorado.
The above described instructions further disclose a cruise control system which provides the best speed to fly information to the operator of the aircraft. The output of the meter in this "cruise" mode provides a zero condition whenever the aircraft is in the most optimum conditions for movement, such as gliding. The operator need only control air speed to hold the meter needle on zero as he flies or cruises between thermals. If the meter reads up, the operator pulls back on the stick control while if the meter reads down, the operator pushes forward on the stick control.
In operation, the RATE OF CLIMB mode is used whenever it is desired to climb within a thermal since the absolute rate of climb is important especially near ground levels. To determine whether to continue climbing or to leave a thermal and to help compute performance while cruising a separate averaging indicator can be used to provide the average rate of climb or sink in a given time frame. However, when searching for a thermal, it is important to have the meter in the NETTO mode to read the rate the vertical air is moving. And finally, in order to minimize the fatigue of the operator and to allow for minimum concentration, once the climb has been made and the aircraft leaves the thermal, the CRUISE mode is used since all the operator need do is either slow or speed up the aircraft in order to be in the optimum flying conditions.
Numerous prior art patents have been issued on various devices for accurately measuring only the rate of change of aircraft movement. Such prior art approaches include the following issued patents:
W. angst et al., U.S. Pat. No. 2,531,492 issued on Nov. 28, 1950; PA1 Anastasia, U.S. Pat. No. 2,718,783 issued on Sept. 27, 1955; PA1 Rusk, U.S. Pat. No. 2,931,221 issued on Apr. 5, 1960; PA1 Summerlin, U.S. Pat. No. 2,970,471 issued on Feb. 7, 1961; PA1 McLane, U.S. Pat. No. 3,055,214 issued on Sept. 25, 1962; PA1 Escobosa, U.S. Pat. No. 3,196,691 issued on July 27, 1965; PA1 Hattendorf, U.S. Pat. No. 3,276,255 issued on Oct. 4, 1966; PA1 Feuer, U.S. Pat. No. 3,572,115 issued on Mar. 23, 1971; PA1 Andresen, Jr., U.S. Pat. No. 3,683,690 issued on Aug. 15, 1972; PA1 Bullard, Jr. et al., U.S. Pat. No. 3,703,828 issued on Nov. 28, 1972; PA1 Kosakowski et al., U.S. Pat. No. 3,726,138 issued on Apr. 10, 1973; PA1 Melsheimer, U.S. Pat. No. 3,789,661 issued on Feb. 5, 1974; and PA1 Greene, U.S. Pat. No. 3,885,430 issued on May 27, 1975.
All of the above prior art patents relate to various design improvements in rate of climb meters primarily directed toward speed of response, accuracy or both features. The device taught by the Feuer patent utilizes a linear pressure transducer and the rate of climb signal is developed electronically by differentiating a static pressure signal and solving a specific equation. The rate of climb sensor taught by Kasakowski et al. teaches the use of a solid state pressure transducer to obtain the rate of climb signal from a digital pressure rate sensor system. The Schwartz apparatus utilizes two pressure sensitive transistors having applied thereto static outside pressure as well as a reference pressure in an air chamber.
In view of the foregoing, while rate of climb meters are known in the prior art and include the taking of the derivative of a developed electrical signal, as well as utilizing pressure sensitive transistors, there is no teaching in the prior art of the aircraft instrument of the present invention wherein a pair of absolute pressure transducers are used to sense both altitude change and airspeed change, combining these outputs, and then taking the derivative of the combined output in order to develop a single signal representative of the rate of climb. Furthermore, none of the above prior patented approaches teach the use of electronically determining the rate of vertical movement of air outside of the aircraft due to thermal conditions or of providing an indication of the best speed to fly conditions. In addition, an optional provision is made to the present invention to provide an average indication of the rate of climb.